Jimmy Garoppolo and Kirk Cousins, at one point last year projected to reunite with 49ers head coach Kyle Shanahan in San Francisco, will share the spotlight when the NFL’s only unbeaten team in December 2017 opens against a club that stood four quality quarters from making the Super Bowl.

The meeting will be the first between these teams since the 2015 opener, when the 49ers rolled to a 20-3 home win.

Garoppolo joined a staggering 49ers team in an in-season trade with New England last Halloween, then quickly secured the honor of being Shanahan’s quarterback of the future with a league-best 5-0 finish that featured wins over one playoff contender and two division champs.

That put the former four-year Patriots backup in a position to cash in, and he did just that when the 49ers, after having finished a 6-10 season, locked up the 26-year-old with a five-year, $137.5 million contract that made him — for a few days, anyway — the highest-paid player in NFL history.

Before Garoppolo’s explosion onto the scene in December, Cousins had been linked to the 49ers as he played out his final season with the Washington Redskins, throwing for more than 4,000 yards for a third consecutive season.

But with San Francisco out of the market for a franchise quarterback, the Vikings, champions of the NFC Central at 13-3 behind Case Keenum, won a bidding war for the most coveted free agent on the market, getting Cousins to sign a three-year, $84 million guaranteed deal that trumped Garoppolo’s deal by $500,000 a season.

Cousins got the better of the pre-Garoppolo 49ers when he passed for 330 yards and two touchdowns in a 26-24 Redskins victory in Week 5 last season.

The 30-year-old is unconvinced his experience with having seen the Shanahan-coached 49ers defense will help him in his Vikings debut.

“I’ve gone against this defensive scheme several times. It doesn’t make you feel like you’ve got it all figured out,” Cousins insisted. “If knowing certain players or certain coaches was the difference-maker, then you wouldn’t see some of these guys have success so much when their coaches leave. At the end of the day, you’ve just got to go out and play.”

Cousins will be surrounded by big-time weapons in game-breaking running back Dalvin Cook, dependable tight end Kyle Rudolph and one of the league’s best 1-2 wideout tandems in Adam Thielen and Stefon Diggs. Diggs is looked at as the deep threat in a new-look offense that underwent major changes beyond Cousins when offensive coordinator Pat Shurmur was named head coach of the New York Giants.

That group will be attacking a defense without standout linebacker Reuben Foster, out on suspension, but with Richard Sherman making his San Francisco debut after having missed most of last season in Seattle with an Achilles injury.

The 49ers also will be a man down on offense with the preseason loss of running back Jerick McKinnon, signed away from the Vikings in March, to a season-ending knee injury.

“Since the day we signed him, we’ve been game-planning for Minnesota,” Shanahan said of McKinnon. “So I’m not going to lie: It changes things pretty drastically. When you go for ... your first target in free agency, you have a plan on how to use him, especially going into Week 1.”

One player the Vikings admit they’re game-planning for is speedy wide receiver Marquise Goodwin. Head coach Mike Zimmer first noticed Goodwin when he went to the University of Texas to work out defensive backs matched against Goodwin’s Olympic-class speed. Goodwin averaged 17.2 yards per reception in 2017 in his first season with the 49ers and had a definite connection with Garoppolo.